Well I just bought portal yesterday, beat it in 3 hours today, but it was still a very fun game and was worth the 20$. I realized my mistake afterwards, because now I am looking into either getting Bioshock or Team Fortress 2...Which if I do get TF2, I probably should've just gotten the Orange Box which would've been cheaper, with more games.

Bioshock is awesome. Bioshock is also singleplayer and once you finish it you might go through a second time but I can't see many people playing through more than twice. Team Fortress 2 on the other hand is an absolute blast and due to new content from valve along with user created content, has huge replayability.

I vote TF2

__________________"The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age."

Get the Orangebox or TF2, fun game, great online...
I hated bioshock... it was really repetative, showed no real innovation, the music sickened me, it was just way over hyped and it failed, after you beat lock it up and throw away the key, you won't touch it again...